A prior art method for measuring the dimensions and orientation of an object which is of particular interest here relies on the use of unrectified or oblique aerial panoramic photography and rectified aerial photography. Unrectified photography is aerial photography where the lens of the camera is tilted away from vertical or z-axis toward the direction of flight or x-axis (usually by more than 3.degree.) and the lens is swept from side to side or about the y-axis. The latitude, heading, tilt of the camera, and focal length of the camera are constantly recorded as the film is being shot and afterwards tabulated for reference to each frame of the photography. Rectified photography is the transformation of the unrectified photography to an equivalent vertical photograph where a true horizontal relation in an x-y plane between points on the photographic image and a ground or map coordinate system is obtained.
In accordance with this prior art method, the unrectified photograph is first scanned for features of interest using a Bausch and Lomb "240 Zoom" stereomicroscope with a magnification of 10.times.. Once a feature of interest is located, the zoom 240 scope is moved out of the way and the same feature is relocated on the unrectified photograph with a 40 power microscope having a reticle which measures in increments of 0.001 inch. Using this reticle, a height measurement of the feature image is made in thousandths of an inch. Thereafter, a special template is used to locate the position of the feature on the unrectified photography by the parameters of obliquety and these photo coordinates are recorded. The parameters of obliquety are measured in angular degrees from a true vertical position. Each angle in "x" and "y" measurement has a unique scale factor which is determined for each location of each photo from a table of scale factors.
With this information, the actual height of the object above the ground in feet is determined using the following formula: ##EQU1## where ground distance in the height above the ground in feet of the top of the object; altitude is the height of the camera above the ground in feet; scale factor is a predetermined factor for determining heights for each angle in "x" and "y" directions; image distance/12 is the measured image displacement of the height of the object in inches divided by 12 to convert the measurement to feet; and focal length is the focal length of the camera taking the photograph in feet. This formula is used only for determining heights from unrectified photographs and must be used for each feature image of interest.
Next, in order to obtain the length, width and orientation of the feature, the feature must again be located on the rectified photograph. It is virtually impossible to take length and width measurements and orientation measurements from unrectified film because of the complexity of the formulas and methods for taking the measurements. With rectified film, distortions have been taken out with regard to the correct position of features although vertical distortion still exists. Using a seven power Bausch and Lomb magnifier with a scale having ticks marked off in five thousandths of an inch increments, the feature image length and width are measured, if possible. If they are measureable, these dimensions are then multiplied by a factor determined from the scale of the photograph and recorded. Of course, if these dimensions are not capable of being measured on the rectified photograph because of loss of resolution, the feature cannot be measured and the time spent so far has been wasted. The needed features must then be guessed at or obtained through a very complex measuring procedure on the unrectified film. Assuming that the feature dimensions are recorded, the feature is then relocated on the rectified photograph and its oreentation or degrees from true north are determined by the use of a clear plastic protractor oriented to grid north. After this long process, hopefully all information on the feature is complete. Then, this long and time consuming procedure must be repeated for each feature of interest on the photograph, and the disadvantages of the procedure are evident.
In so far as the viewing and measuring of an object or feature is concerned, the prior art has disclosed many devices to aid in this process. For example, in U.S. Pat. No. 3,119,185 to Gray, an optical and magnifying comparator is disclosed having a reticle very close to the feature to be measured. The use of a reticle with a cross-hair has also been disclosed in a prior art telescopic gun sight as shown in U.S. Pat. No. 2,997,916 to Friedman et al. and in a stereogoniometer as shown in U.S. Pat. No. 3,535,043 to Hong. The stereogoniometer disclosed in the Hong reference also includes a protractor scale with an adjustable cross-hair. There has also been disclosed, in U.S. Pat. No. 4,051,483 to Suzuki, a system for measuring and recording the three dimensional configuration of an object using moiretopography and a computer. The location of a feature on a photograph has also been performed using two stereo images. Such a system is described in U.S. Pat. No. 3,750,293 to Forrest.